For many years the footwear made of plastics and the footwear made of polymers with inner liner made of woven or nonwoven fabric is known, for example the patent, GB1423217 granted to KOHKOKU CHEMICAL IND CO, discloses a boot molded by injection including a sock (3) made of an elastic fabric coated with synthetic resin and having a pattern or color printed on the synthetic resin layer and an outer layer molded by injection (7) that completely covers the sock. The layer (7) is made of a transparent or translucent synthetic resin. Preferably the sock (3) is cut from a sheet material and consists of a woven fabric of elastic fibers, which have been coated with foamed polyvinyl chloride and have a printed pattern on the PVC coating.
It is also known the document EP2875941 A1, of Ferreira Alves, which discloses that the inner liner is an inseparable part of the footwear wherein the internal liner is a woven and laminated tubular sock with a polyurethane film. The sock is placed on the core or inner mold of the footwear. Due to the fact that the sock material is covered with polyurethane it is that the polymeric material (polyurethane foam), with which is preferably made the boot, does not pass the sock towards the mold core and thus, the inner liner remains only as woven fabric.
Prior to this invention, the inner liner was characterized by the cutting of two halves of the fabric and the laminated film and then they were sewn leaving only the top for its introduction into the mold core.
It is important to point out that in the case of GB'217 patent, the footwear comprises an upper part and a lower part which are joined by sewing or gluing, which is not the case of the EP' 941 patent which is casted so that the sole and the footwear body forms a single piece.
The U.S. Pat. No. 3,823,493, refers to a boot with an inner liner made of fabric which is coated with an impermeable plastic film such as PVC, see FIG. 8 of this document.
Finally, the document GB369041, refers to a method for manufacturing rubber footwear comprising a coating made of a single piece of woven with areas having different stitches to give the approximate shape of a foot. The different parts of the boot are constructed by vulcanizing the woven fabric sock placed on a shoetree.
It is considered that the first two documents represent the closest state of the art.
In general, both processes are very similar and consist of liner a heart with an open tube by a first end and cast the polymeric material. Once the heart of the mold is lined this is closed and the selected polymer is casted by injection at an enough pressure to fill the cavity formed between the tube (so called sock) and the movable parts of the mold. Once the material is injected this is allowed to cool and solidify so as to adopt the shape of the mold. It is important to mention that due to the texture and material of the sock, the polymeric material does not reach the heart of the mold and therefore, the inner liner of the footwear is a fully formed face of the selected fabric.
The outside of the footwear is the same polymeric material which while technically results in a waterproof material that prevents the passage of liquid into the footwear, the appearance is not aesthetic but the polymer used is the most attractive color.
Besides the aesthetic problem, there is a drawback with this type of footwear since it is not possible to impart them properties such as antifungal, fire retardant, etc.
Previously if it was desired to give a colorful appearance or a specific pattern to the outside of the boot it was necessary to use a transparent polymeric resin, as shown in GB 1,423,217.
As mentioned above, the prior art overcome the obstacle of the material permeation with which the boot is prepared by using a laminate to the sock fabric and/or modifying the composition of the casting material so that its viscosity prevents the pass thereof through the fabric while the present invention has saved this objection by using suitable fabrics which have characteristics such as cotton fabric which absorbs up to 27 times its weight in water according to the guide “Sewing and Craft Alliance”. The polyester having high elasticity and high stability and consistently form; has a low amplification (the fiber appears smooth and rod-shaped usually is circular in cross-sectional areas); are extremely strong (tenacity=3.6 to 4.6 g tex 0.35 to 0.45 in tex and abrasion resistant); stretch resistant, extensible and does not easily wrinkle; the fibers are not attacked by bacteria, mold or moths; It is more resistant than any fiber to sunlight. In its chemical properties the polyester has good resistance to weak mineral acids; excellent resistance to oxidizing agents.